The Influenza virus is a common virus contracted usually in winter months. Mostly sufferers are able to develop an immune response and fight the infection within days, however some more severe cases can lead to respiratory complications and furthermore death. Individuals with weaker immune systems are more vulnerable and susceptible to the infection as they are not able to produce a sufficient defence against the replication of the virus within the body. The virus has previously been the major cause of epidemics in the history of medicine worldwide such as the Spanish flu, however there has been a discovery of the influenza virus vaccine which has been designed to prevent infection. The vaccine is capable of lowering levels of infection, nevertheless with all medical breakthroughs there are negative aspects.
The Influenza vaccination involves modifying a particular influenza strain into a form which still mimics the original behaviour of the influenza organism, but disables the virus to develop into influenza within the body by reducing its pathogenicity. (roitts) In this instance the body prompts an immune response to the modified weakened form of the influenza vaccine, allowing our bodies to store this response in our immunological memories. Therefore when the actual virus does attack our immune system in its full form, the response prompted will be highly efficient in killing the virus.
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Increasingly people are being infected or vaccinated against the influenza virus, however, the virus is so prevalent amongst humans that the viral strand is able to mutate and become stronger every year. The virus mutates against selection pressures into forms which are recognised as different antigens compared to the original viral strain by the immune system. The immune system is therefore broducing two different immune responses for different strains. Therefore every year, drug companies predict the most abundant strands of the season a few months before the winter months and design a vaccine incorporating these strands. For example the most recent strand in the UK is the H1N1 strand more commonly known as 'Swine Flu.'
There are different forms of the influenza vaccine; there is the injection and the nasal spray. There are two forms of vaccine, the attenuated vaccine also known as the 'live' vaccine (LAIV), which involves the influenza viral cells to be cultured and grown in eggs to eventually develop into the less virulent form. The disadvantage associated with LAIV is that if the virus is not sufficiently inactivated, it could cause infection once injected, producing a very large risk for the individual. The other type of vaccination is the inactivated trivalent influenza vaccine (TIV). This is where the viral influenza cells are killed and then used for vaccination. The current influenza vaccine in the UK consists of this trivalent form. This allows the vaccination to protect the immune system against three strands. The three strands used are the most recently actively seen infecting in the population, this consists of the H1N1 strain, which is responsible for the swine flu, the Influenza B strain and H3N2, (influenza A). This vaccination will only provide protection for these three strands, the disadvantage being if an individual were infected with any other influenza strain other than these three, it would not be sufficient enough for protection. This trivalent vaccine destroys the viral cells preventing them from replicating, but keeping the virus capsid proteins intact, enough to be recognized by the immune system as a foreign antigen and to evoke an immune response without actually being infected with the true viral form.
There are many advantages to the influenza vaccine; this includes the obvious 'protection' against influenza through the winter months. Once vaccinated, there is no possible chance of catching influenza, this is an advantage of using the inactivated trivalent form of the vaccine as the viral cells are killed and so there is no chance of contracting the virus from the vaccination itself. Whereas the live attenuated vaccine may have a risk of doing so if the cells are not thoroughly inactivated.
The vaccine dramatically reduces the risk of pneumonia and hospitalization in high-risk patients. High-risk patients are regarded as pregnant women, the elderly and patients suffering from certain diseases which may not be able to bring about a strong enough immune response if they were infected. Currently there are debates as to whether young children should be protected using this vaccine, the dilemma associated with this is whether young children are at a high enough risk of being infected in the first place. The risk of children being infected is fairly low and compared to the cost of vaccinating every child under the age of five is not worthwhile. The overall cost may not be worth this small risk as this vaccine is very expensive. Although protection is guaranteed, this only lasts for a year or however long that particular strand prevails in the community, this could be months or years before it becomes dormant or mutates. Therefore vaccinating everyone in a population is not beneficial as it would only encourage the mutation of the current strains into new unknown strains, which would require large quantities of further research, money and time to develop new vaccinations. This is a lengthy and costly process for the medical research field.
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The influenza virus causes an overall immune response which eliminates the virus from the body in order to protect itself. The way in which it does this is imitated by the vaccine; however the vaccine is able to do so in a more efficient manor and without the production of symptoms. The cellular immune response which is activated when infected with the virus causes dendritic cells to present the foreign antigen (influenza virus) on T cell receptors (TCR). This then causes T helper cells (CD4+) and cytotoxic T cells (CD8+) to produce effector cells which produce cytokines. CD4+ cells help to activate the cytotoxic T cells which help in killing the infected epithelial cell. The T helper effector cell also contributes to the humoral response. The humoral response is when the foreign influenza antigen is detected on the B cell, causing the B cell to develop into the antibody secreting plasma cells in order to produce highly specific antibodies to eliminate the influenza virus. This is known as the primary response. The primary response can be seen in individuals, when experiencing symptoms of influenza, such as fever, cough, headache, fatigue and body aches. Here the immune response is being conducted and as a result causing these symptoms to persist.
The secondary immune response is where the B cells are able to recognise amino acid sequences of the epitopes of the antigens and have a greater recognition of these specific influenza antigens. These are known as the memory B cells, so if the immune system were to be attacked again there would be greater number of antibodies already present, and a fast production rate of these specific antibodies in order to eliminate the virus. The influenza vaccine allows the primary response to be skipped; it is a slow process in producing antibodies, therefore making the influenza vaccination a very efficient option for those at risk. By allowing the body to produce the specific antibodies to the specific strains at a much faster rate it eliminates the slow response.
Overall the benefits of the vaccine are extremely beneficial to public health as it provides a strong immunity against the influenza virus. It lowers general costs for the NHS, as fewer patients require appointments and treatments from the GP, it also lower rate of sickness from work and it improves health within the country as it is less likely to infect at a fast rate if immunity is already present within the community. The only disadvantages are the costly aspects and due to the current vaccines trivalent nature it can only provide immunity to three strains present. Herd immunity in this influenza virus can not be established. By doing do would require over 70 % of the community to be vaccinated and so would only force selection pressures against the virus, causing it to mutate further into new strains. The way in which the vaccine is distributed, is ideal for optimum results and the benefit is greater than the possible risks associated with the vaccination.